It sounds from the post that actual marker light assemblies are required, not bulbs. The commonly available 12v light assemblies that I have been able to find use a different bulb base that the 24v bulbs seem to need, and the only assemblies that I have been able to find are OEM. My bulbs need a BA15d socket. If your assemblies are OK but you just need new amber and red lens covers I would just call Prevost and order them. Prevost seems to be very good on part availability and pricing.

Got the bulbs @ Grainger & not cheap. Going to get with Prevost, but after finding out that Prevost's Goodyear air bags are $173.34 & MCI has them for $91. I am a little bit ascared of their prices now. MCI doesn't have what I need, but they are very helpful & did try.

I have been pondering the issue of updating marker lights on my MCI for about a year and a half now, every since I started to see failed corroded bulb sockets. The fixing screws are all corroded as well, so replacing would mean grinding out the screws, getting the remnants out of the roof skin and then scabbing on some non-OEM replacement if I was too cheap to spring for new MCI assemblies, which I in fact am (too cheap, that is). So I have been searching high and low for a suitable 24v LED solution, and have found none. So I knew that Grote makes a new mini-marker light called the Micro Nova in red, white and amber, in 24v. It struck me that all I really need to do is replace the failed sockets in my lights, but they are bonded in and I can't get the old sockets out in a way that lets me replace them with a new socket. So today I opened up a light on the bus and had a bit of a measure-up, and I can remove the sockets and replace them with one of these Micro Nova LED's, which are 3/4" in diameter. If I get the white light ones they can shine through the OEM lens covers, and apparently they are very bright, so it should be good. I just ordered one from my local NAPA as a test subject, if it works I will order more on-line - $26 here in town, and $16 shipped out of Los Angeles. If this works, it may be a useful project.